ICESCAPE scientist Karen Frey taking optical measurements in a melt pond, with the U.S. Coast Guard Cutter Healy on the background. Photo: NASA’s Goddard Space Flight Center/Kathryn Hansen.
Given everything marine researchers know about phytoplankton, a type of algae, no one expected to find some of the world’s largest blooms beneath Arctic sea ice. But this is exactly what scientists stumbled on during an ICESCAPE expedition in the Chukchi Sea, which is examining the massive impacts of climate change in the region. Researchers recorded a 100 kilometer (62 miles) long bloom underneath the Arctic ice pack that was four times richer than adjacent ice-free waters.
“This is like finding the Amazon rainforest in the middle of the Mojave Desert,” said Paula Bontempi, NASA’s ocean biology and biogeochemistry program manager, in a press release. “We embarked on ICESCAPE to validate our satellite ocean-observing data in an area of the Earth that is very difficult to get to. We wound up making a discovery that hopefully will help researchers and resource managers better understand the Arctic.”
The researchers hypothesize that the plankton are thriving off sunlight magnified through pools of water atop ice sea. As sea ice melts, water collects on the top of the pack, focusing sunlight into nutrient-rich waters just below the ice and creating an explosion of life. Prior to this, researchers had assumed that the sea ice would have blocked any sunlight, making it impossible for plankton to thrive.
The under-ice plankton bloom also turned out to be particularly fecund. They doubled in number more than once a day, while plankton in open Arctic waters only double every two to three days.
“At this point we don’t know whether these rich phytoplankton blooms have been happening in the Arctic for a long time and we just haven’t observed them before,” said Kevin Arrigo leader of the ICESCAPE mission and lead author of a new study describing the phenomenon in Science. “These blooms could become more widespread in the future, however, if the Arctic sea ice cover continues to thin.”
Climate change due to anthropogenic greenhouse gas emissions is warming the Arctic faster than anywhere else on Earth. One of the impacts has been a decline in old ice–which doesn’t melt seasonally–and an increase in younger and thinner ice, which may be facilitating these below ice plankton blooms.
Plankton play an important role in sequestering carbon dioxide, so if the blooms are common it could provide new insight into how much carbon Arctic ecosystems are soaking up.
When light reaches the nutrient-rich waters under the Arctic ice cap, it creates the perfect environment for phytoplankton to bloom. Credit: Don Perovich/U.S. Army Cold Regions and Engineering Laboratory.
Climate change has rapidly shrunk Arctic sea ice over the past thirty-plus years. Images showing the Arctic sea ice minimum in September of 1979 (the year satellites started recording sea ice extent) and in September of 2011. Credit: NASA.
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